Diverters are mounted to offshore drilling rigs below the rig floor for use in early stages of drilling. A support housing mounts below the rig floor and has a lateral flowline outlet for directing mud flow when the diverter is closed. The housing is a tubular member with an axial bore. A diverter body is secured to the upper end of a riser, is lowered through the rotary table and lands in the housing. The diverter body has lateral flow openings that are axially aligned with the lateral flowline outlet. A pair of seals are located above and below the lateral flowline outlet.
The seals seal the diverter body to the diverter housing. One type of prior art seal comprises a bulk seal having cylindrical inner and outer diameter walls. The bulk seal is bonded to upper and lower metal rings. After the diverter body lands, hydraulic pressure is applied to the inner diameter of each of the seals to deform the elastomer into sealing engagement with the diverter housing. While workable, improvements are desired.